My advice on this is to get hold of a copy of the 'Stones Justices Manual' and have a read, and a read, and another read- to make sure you are comfortable in making use of the exemption, and that worst case senario you would be happy to defend your use of the exemption in a court of law. Remeber that road traffic Law is not 'joined up' so make sure that you would not fall foul of some other piece of road traffic law. 'Stones' is a very good bedtime read, and it's what the criminal courts use! It contains both the relevent statue law, and also relevent 'case law' Usually it is the case law which is the important part as this gives the legal interpretation on the statute law.... Unfortunatly, the only case law I could find for MPV is 'Creek v Fossett, Eccles & Supertents Ltd, and it was a decision made under previous legislation. Remeber that the likes of DVLA, ect may give you their 'take' on an issue- However, only the courts can decide on the legal interpretation of statute law!!!